Carbon quantum dots / aqueous polyurethane composite fluorescent powder and preparation method thereof

Abstract

The application discloses carbon quantum dots / water-based polyurethane composite fluorescent powder and a preparation method thereof, and belongs to the field of carbon quantum dots modification. The preparation method of the carbon quantum dots / water-based polyurethane composite fluorescent powder utilizes the acidity of a carbon quantum dots solution to make the positive and negative charges of an anionic water-based polyurethane unbalanced, breaks emulsion coagulation, and makes the carbon quantum dots solution and the water-based polyurethane emulsion coagulate and compound based on a coagulation composite method, so that the carbon quantum dots / water-based polyurethane composite fluorescent powder is prepared. The preparation method is simple in operation route and low in cost. The carbon quantum dots / water-based polyurethane composite fluorescent powder is high in light stability, can be uniformly dispersed in the water-based polyurethane, and cannot cause phenomena such as agglomeration quenching.

Description

Technical Field

[0001] This invention belongs to the field of carbon quantum dot modification, and in particular to a carbon quantum dot / waterborne polyurethane composite phosphor and its preparation method. Background Technology

[0002] Carbon quantum dots, or simply carbon dots, are novel carbon-based zero-dimensional materials composed of near-spherical carbon particles with dimensions below 10 nm. They possess excellent optical properties, low biotoxicity, wide availability, environmental friendliness, excellent dispersibility, and chemical stability, making them promising candidates for applications in bioimaging, analytical detection, chemical analysis, catalyst preparation, and energy development. Waterborne polyurethane, also known as water-dispersible polyurethane, is a novel system that uses water instead of organic solvents as the dispersion medium. It offers advantages such as being pollution-free, having low odor, being safe and reliable, possessing excellent mechanical properties, good compatibility, and being easy to modify.

[0003] The synthesis of carbon quantum dots and the preparation of functional polymers are two areas in modern materials chemistry where great success has been achieved. In recent years, research focusing on combining the advantages of carbon quantum dots with polymers to prepare novel functional composite materials has received increasing attention. Currently, the most researched area is the preparation of carbon quantum dot-based phosphors by mixing carbon quantum dots with polymers such as polyvinyl alcohol and starch. Waterborne polyurethane materials are a relatively mature polymer material, possessing good optical transparency, wear resistance, and simple synthesis methods. Furthermore, the mechanical properties and elasticity of the material can be adjusted by regulating the ratio of hard and soft segments, and it is currently widely used in various aspects of life. However, research on endowing waterborne polyurethane with luminescent properties is still lacking. This has promoted the combination of carbon quantum dots with unique optical properties with waterborne polyurethane, driving the development of luminescent materials. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a carbon quantum dot / waterborne polyurethane composite phosphor and its preparation method.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A method for preparing a carbon quantum dot / waterborne polyurethane composite phosphor: an acidic carbon quantum dot solution and a waterborne polyurethane are mixed at a mass ratio of 1:10, and the carbon quantum dot solution and the waterborne polyurethane emulsion are coagulated and composited to obtain a carbon quantum dot / waterborne polyurethane composite phosphor.

[0006] Furthermore, the carbon quantum dot solution is prepared by the following method: Citric acid and ethanolamine were dissolved in dilute sulfuric acid solution at a molar ratio of 1:1 to obtain a precursor, which was then subjected to a hydrothermal reaction at 200°C for 5 hours. After the hydrothermal reaction was completed, the reaction solution was cooled to room temperature, centrifuged, and dialyzed to obtain a full-color carbon quantum solution.

[0007] Furthermore, the carbon quantum dot solution is prepared by the following method: Citric acid and aniline blue were dissolved in a mixture of dilute sulfuric acid and ethanol at a mass ratio of 300:1 to obtain a precursor, which was then subjected to a hydrothermal reaction at 200°C for 5 hours. After the hydrothermal reaction was completed, the reaction solution was cooled to room temperature, centrifuged, and dialyzed to obtain a green carbon quantum solution.

[0008] Furthermore, citric acid and p-phenylenediamine were dissolved in dilute sulfuric acid solution at a molar ratio of 1:1 to obtain a precursor, which was then subjected to a hydrothermal reaction at 200°C for 5 hours. After the hydrothermal reaction was completed, the reaction solution was cooled to room temperature, centrifuged, and dialyzed to obtain a yellow carbon quantum solution.

[0009] Furthermore, dialysis was performed using a dialysis bag with a molecular weight cutoff of 1000 Da for 24 hours, with the water changed every 6 hours.

[0010] Furthermore, citric acid and Nell Blue were dissolved in a mixture of dilute sulfuric acid and ethanol at a mass ratio of 600:1 to obtain a precursor, which was then subjected to a hydrothermal reaction at 200°C for 5 hours. After the hydrothermal reaction was completed, the reaction product was cooled to room temperature and then centrifuged and chromatographically analyzed to obtain a red carbon quantum solution.

[0011] Furthermore, column chromatography was performed using petroleum ether and anhydrous ethanol in a volume ratio of 5:1.

[0012] Furthermore, the waterborne polyurethane is of the polycarbonate type and has a solid content of 30%.

[0013] A carbon quantum dot / waterborne polyurethane composite phosphor was prepared according to the preparation method of the present invention.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a method for preparing carbon quantum dot / waterborne polyurethane composite phosphors. This method utilizes the acidity of the carbon quantum dot solution to cause an imbalance of positive and negative charges in the anionic waterborne polyurethane, leading to demulsification and aggregation. Based on an aggregation-composite method, the carbon quantum dot solution and the waterborne polyurethane emulsion are aggregated and composited to prepare the carbon quantum dot / waterborne polyurethane composite phosphor. The preparation method of this invention is simple in operation and low in cost; the waterborne polyurethane uses water as the dispersion medium, making it safe and environmentally friendly, and promoting the development of sustainable and eco-friendly materials.

[0015] Furthermore, using dilute sulfuric acid as the main reaction solvent, full-color carbon quantum dots with amino and hydroxyl groups on their surface were successfully prepared in one step by hydrothermal method. As a raw material, they were added to waterborne polyurethane. The acidic carbon quantum dot solution caused the charge imbalance of the waterborne polyurethane, which demulsified and agglomerated to form full-color phosphor.

[0016] The carbon quantum dot / waterborne polyurethane composite phosphor of this invention exhibits strong photostability and can be uniformly dispersed in waterborne polyurethane without agglomeration or quenching. The highly polar urethane groups in the polyurethane have no impact on fluorescence performance. Carbon quantum dots impart fluorescence properties to the waterborne polyurethane, while the waterborne polyurethane imparts high wear resistance to the carbon quantum dots. The two complement each other, resulting in a carbon quantum dot / waterborne polyurethane composite phosphor with uniform particle size and elasticity. Attached Figure Description

[0017] Figure 1 Infrared spectral images of carbon quantum dots from Examples 1-4; Figure 2 Fluorescence test images of carbon quantum dots in Examples 1-4; Figure 3 The UV absorption spectra of carbon quantum dots in Examples 1-4 are shown. Figure 4 The CIE chromaticity diagrams of carbon quantum dots in Examples 1-4 are shown, where (a) to (d) correspond to Examples 1-4, respectively. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] The present invention will now be described in further detail with reference to the accompanying drawings: This invention utilizes an acidic carbon quantum dot solution to demulsify and coagulate aqueous polyurethane, resulting in physical cross-linking and composite coagulation. The carbon quantum dot aqueous polyurethane phosphor prepared by this coagulation and composite method is non-toxic, pollution-free, simple to operate, safe, and quick. The coagulation and composite speed of the aqueous polyurethane and acidic carbon quantum dots is controlled by adjusting the addition rate of carbon quantum dots and the stirring speed, thereby controlling the particle size of the phosphor and producing a phosphor with uniform size and good elasticity. This phosphor can be widely used in light-emitting devices, fluorescent fillers, functional additives, and other fields.

[0021] Example 1 Step (1): Preparation of blue carbon quantum dots Using citric acid as the carbon source and ethanolamine as the nitrogen source, 1 mol of citric acid and 1 mol of ethanolamine were dissolved in 20 ml of 2.8 mol / L dilute sulfuric acid solution. The fully dissolved and mixed solution was then transferred to a polytetrafluoroethylene (PTFE) liner. The PTFE liner was sealed in the reaction vessel, and the mixture was heated in an oven at 200°C for 5 hours, after which heating was stopped. After the reaction was complete, the oven temperature was allowed to cool naturally to room temperature. The reaction vessel was then removed, and the solution was poured out to obtain the initial carbon quantum dot product solution. After centrifugation to remove the precipitate, the solution was dialyzed using a dialysis bag with a molecular weight cutoff of 1000 Da for 24 hours (with water changed every 6 hours) to obtain a blue carbon quantum dot solution. Step (2): Preparation of blue carbon quantum dot / waterborne polyurethane composite phosphor The prepared blue carbon quantum dot solution was uniformly mixed and dispersed with waterborne polyurethane with a solid content of 30% at a mass ratio of 1:10, ultrasonically dispersed for 1 h, and then freeze-dried to obtain the blue carbon quantum dot / waterborne polyurethane composite phosphor.

[0022] Example 2 Using citric acid as the carbon source and aniline blue as the nitrogen source, and a 1:1 mixture of 2.8 mol / L dilute sulfuric acid and ethanol as the solvent, 3 g of citric acid and 0.01 g of aniline blue were dissolved in 20 ml of the solvent. The fully dissolved solution was then transferred to a polytetrafluoroethylene (PTFE) liner, which was sealed in the reactor. The reactor was heated at 200°C for 5 hours, after which heating was stopped. After the reaction was complete, the reactor was allowed to cool naturally to room temperature. The solution was then removed and poured out to obtain the initial carbon quantum dot product solution. After centrifugation to remove the precipitate, the solution was dialyzed using a dialysis bag with a molecular weight cutoff of 1000 Da for 24 hours (with water changed every 6 hours) to obtain a green carbon quantum dot solution.

[0023] The prepared green carbon quantum dot solution was uniformly mixed and dispersed with waterborne polyurethane with a solid content of 30% at a mass ratio of 1:10, ultrasonically dispersed for 1 h, and then freeze-dried to obtain green carbon quantum dot / waterborne polyurethane composite phosphor.

[0024] Example 3 Using citric acid as the carbon source and p-phenylenediamine as the nitrogen source, 1 mol of citric acid and 1 mol of p-phenylenediamine were dissolved in 20 ml of 6.1 mol / L sulfuric acid solution. The fully dissolved and mixed solution was then transferred to a polytetrafluoroethylene (PTFE) liner. The PTFE liner was sealed in the reaction vessel, and the mixture was heated in an oven at 200°C for 5 hours, after which heating was stopped. After the reaction was complete, the oven temperature was allowed to cool naturally to room temperature. The reaction vessel was then removed, and the solution was poured out to obtain the initial carbon quantum dot product solution. After centrifugation to remove the precipitate, the solution was dialyzed using a dialysis bag with a molecular weight cutoff of 1000 Da for 24 hours (with water changed every 6 hours) to obtain a yellow carbon quantum dot solution.

[0025] The prepared yellow carbon quantum dot solution was uniformly mixed and dispersed with waterborne polyurethane with a solid content of 30% at a mass ratio of 1:10, ultrasonically dispersed for 1 h, and then freeze-dried to obtain the yellow carbon quantum dot / waterborne polyurethane composite phosphor.

[0026] Example 4 Using citric acid as the carbon source and Nell Blue as the nitrogen source, and a 1:1 (v / v) mixture of 2.8 mol / L dilute sulfuric acid and ethanol as the solvent, 6 mol of citric acid and 0.01 mol of Nell Blue were dissolved in 20 ml of the mixture. The fully dissolved solution was then transferred to a polytetrafluoroethylene (PTFE) liner, which was sealed in the reactor. The reactor was heated at 200°C for 5 hours, after which heating was stopped. After the reaction was complete, the reactor was allowed to cool naturally to room temperature. The solution was then removed, and the initial carbon quantum dot product solution was obtained. After centrifugation to remove the precipitate, a red carbon quantum dot solution was prepared by column chromatography using petroleum ether and anhydrous ethanol at a 5:1 (v / v) ratio.

[0027] The prepared red carbon quantum dot solution was uniformly mixed and dispersed with waterborne polyurethane with a solid content of 30% at a mass ratio of 1:10, ultrasonically dispersed for 1 h, and then freeze-dried to obtain the red carbon quantum dot / waterborne polyurethane composite phosphor.

[0028] See Figure 1 , Figure 1 The images show infrared spectra of carbon quantum dots from Examples 1-4. The blue, green, yellow, and red carbon quantum dots at 3500 cm⁻¹ are clearly visible in the images. -1 The stretching vibration absorption peaks of -OH and -NH2 on the left and right sides, at 1679 cm⁻¹. -1 The absorption peak of the C=O stretching vibration, 1512, and the in-plane deformation vibration of -NH2, 619 cm⁻¹ -1 The rocking vibration absorption peak of -NH2, 1092 cm⁻¹ -1 The absorption peaks of CO stretching vibrations on the tertiary hydroxyl or carboxyl groups indicate that the surfaces of the four types of carbon quantum dots prepared contain abundant -OH and -NH2 groups.

[0029] See Figure 2 , Figure 2 The images show fluorescence test results of carbon quantum dots from Examples 1 to 4. It can be clearly observed from the images that the optimal emission wavelength for full-color carbon quantum dots is 460 nm, for green carbon quantum dots it is 495 nm, for yellow carbon quantum dots it is 570 nm, and for red carbon quantum dots it is 635 nm.

[0030] See Figure 3 , Figure 3 The figures show the UV absorption spectra of the carbon quantum dots from Examples 1-4. The spectra clearly show two significant optical absorption peaks in the 260-280 nm range for the blue, green, yellow, and red carbon quantum dot solutions from Examples 1-4, corresponding to the π→π* and n→π* electronic transitions of C=C and C=N, respectively. Furthermore, the yellow and red quantum dots exhibit significant absorption peaks at 450-500 nm and 500-550 nm, respectively, coinciding with the excitation wavelengths of the yellow (450 nm) and red (500 nm), indicating greater absorption at longer wavelengths.

[0031] See Figure 4 , Figure 4 The CIE chromaticity diagrams of carbon quantum dots from Examples 1-4 are shown in the figures. It can be clearly observed from the figures that the coordinates of the blue carbon quantum dots are (0.186, 0.275), located in the blue region; the coordinates of the green carbon quantum dots are (0.231, 0.415), located in the green region; the coordinates of the yellow carbon quantum dots are (0.448, 0.543), located in the yellow region; and the coordinates of the red carbon quantum dots are (0.676, 0.324), located in the red region.

[0032] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a carbon quantum dot / waterborne polyurethane composite phosphor, characterized in that: Acidic carbon quantum dot solution and aqueous polyurethane were mixed at a mass ratio of 1:10, and the carbon quantum dot solution and aqueous polyurethane emulsion were coagulated and composited to obtain carbon quantum dot / aqueous polyurethane composite phosphor. The carbon quantum dot solution was prepared by the following method: Citric acid and aniline blue were dissolved in a mixture of dilute sulfuric acid and ethanol at a mass ratio of 300:1 to obtain a precursor, which was then subjected to a hydrothermal reaction at 200°C for 5 hours. After the hydrothermal reaction was completed, the reaction solution was cooled to room temperature, centrifuged, and dialyzed to obtain a green carbon quantum solution. Alternatively, citric acid and ethanolamine can be dissolved in dilute sulfuric acid solution at a molar ratio of 1:1 to obtain the precursor, followed by a hydrothermal reaction at 200℃ for 5 hours. After the hydrothermal reaction was completed, the reaction solution was cooled to room temperature, centrifuged, and dialyzed to obtain a full-color carbon quantum solution. Alternatively, citric acid and p-phenylenediamine can be dissolved in dilute sulfuric acid solution at a molar ratio of 1:1 to obtain the precursor, followed by a hydrothermal reaction at 200℃ for 5 hours. After the hydrothermal reaction was completed, the reaction solution was cooled to room temperature, centrifuged, and dialyzed to obtain a yellow carbon quantum solution. Alternatively, citric acid and Nell Blue can be dissolved in a mixture of dilute sulfuric acid and ethanol at a mass ratio of 600:1 to obtain a precursor, followed by a hydrothermal reaction at 200°C for 5 hours. After the hydrothermal reaction is completed, the reaction product is cooled to room temperature, followed by centrifugation and chromatography to obtain a red carbon quantum solution. The waterborne polyurethane is of the polycarbonate type and has a solid content of 30%.

2. The method for preparing carbon quantum dot / waterborne polyurethane composite phosphor according to claim 1, characterized in that, Dialysis was performed using a dialysis bag with a molecular weight cutoff of 1000 Da for 24 hours, with the water changed every 6 hours.

3. The method for preparing carbon quantum dot / waterborne polyurethane composite phosphor according to claim 1, characterized in that, Column chromatography was performed using petroleum ether and anhydrous ethanol in a volume ratio of 5:

1.

4. A carbon quantum dot / waterborne polyurethane composite phosphor, characterized in that, It is prepared according to any one of claims 1-3.

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